Spherical container



Nov. 11, 1958 H. s. DAL'EY SPHERICAL CONTAINER Filed Feb ZONEOFMAX THICKNE 20W OFNORMAL TII/CKNE'SS INVENTOR fi oraoeShDalw' BY ATTORNEY CKoWA/OKZONE 0 M/M TH/CKAE'SS United rates Patent SPHERICAL CONTAINER Horace S. Daley, Clifton, N. J., assignor to Specialties Development Corporation, Belleville, N. J., a corporation of New Jersey Application February 9, 71954, Serial No. 409,053 2 Claims. (Cl. 220-3 The present invention relates to metallic receptacles, such as containers for storing high pressure fluid media, and, more particularly, to an improved spherical con tainer of this type.

Spherical containers usually are made by deep-drawing a pair of substantially hemispherical metallic shells from a circular blank, providing a main discharge outlet at the crown of one of the shells, and securing the shells together at the edges thereof. In cases where the containers are to be used for storing fluid under high pressure, for example, in excess of about 500 pounds per square inch, it is customary to utilize steel shells and to secure them together by welding the same.

In the course of deep-drawing the steel blanks into hemispherical shells, it has been found that the thickness of the shells at thecrown is reduced as much as of the blank thickness. Such reduction of the crown zone thickness is inherent to the deep-drawing operation and cannot be avoided. Consequently, the outlet is provided in the weakest zone of the shell. When high stresses are applied, the material in the immediate vicinity of the outlet is even more highly stressed because of the discontinuity at this zone. This commonly is called stress concentration and is a well recognized phenomenon.

In order to overcome such weakening of the container, it has been proposed to draw the shells from blanks of extra thickness so that the ultimate thickness of the shells at the crown is such that the shells are capable of safely withstanding the stresses applied. This would require that the blank thickness be increased about 10% with the result that the weight of the container is increased about 10%. Since the containers in many cases are used on craft and vehicles where weight must be reduced to a minimum, such an increase in weight is objectionable,

While it is possible to remove excess metal at the zones of greater than required thickness and thereby somewhat reduce the weight of the container, the machining operations involved are costly and thus render this method economically unfeasible.

Accordingly, the present invention aims to overcome the foregoing difficulties in a simple, practical and economical manner.

An object of the present invention is to provide spherical containers of the character described in which stress concentrations beyond a permissible magnitude are eliminated.

Another object of the present invention is to provide such containers without increase in weight thereof.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

"ice.

In accordance with the present invention, the foregoing objects are accomplished by providing a spherical container comprising a pair of substantially hemispherical metallic shells secured together at the edges thereof with one of the shells having a main discharge outlet located between its edge and its crown. These shells have a zone of maximum thickness adjacent the edges thereof, a zone of minimum thickness at the crown thereof and an intermediate zone of an average thickness equal to at least about the thickness of the blank. Thus, by locating the outlet in this intermediate zone, stresses thereat are greatly minimized.

A preferred embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawing, forming a part of the specification, wherein:

Fig. 1 is an elevational view of a spherical container in accordance with the present invention, portions thereof being broken away and shown in section.

Fig. 2 is a schematic longitudinal sectional view of one of the hemispherical shells, illustrating the zones of various thickness on an exaggerated scale.

Referring to the drawing in detail and more particularly to Fig. 1 thereof, there is shown a spherical container comprising an upper substantially hemispherical metallic shell 10, for example, deep-drawn from a circular steel blank, and a lower shell 11 of similar construction. The shells are secured together at the edges thereof, for example, by an equatorially extending weld W to provide a container for storing liquid or gaseous fluid or a mixture thereof under high pressure.

By reason of the shell having been deep-drawn, that is, by forcing a steel blank of uniform thickness through a die having a circular throat by means of a plunger having a generally hemispherical head, the thickness of the shell at the crown is reduced about 10% with respect to the blank thickness and the thickness of the shell adjacent the edge is increased about 10% with respect to the blank thickness. As illustrated in Fig. 2 on an exaggerated scale, the thickness of the shell decreases progressively from the edge to the. crown. The shell may be divided into three zones of thickness which comprise a spherical zone of maximum thickness adjacent the edge, a spherical segmental zone of minimum thickness constituting the crown, and an .intermediate spherical zone of about normal thickness, the average thickness of which corresponds to about the thickness of the blank. The latter zone. is defined by equatorial planes disposed at about ten and about sixty degrees with respect to the plane in which the edge and the weld are located.

In accordance with the invention, at least one of the shells 10 or 11, or both of these shells as shown in Fig. 1, is provided with an outlet opening 12 in the intermediate zone at which a spud 14 is secured, for example, by welding. The axis of the outlet is within this zone, whereby any stress concentrations caused by the opening are within a portion of the shell having at least about a normal thickness.

The ability of the shell to safely withstand such stress concentrations increases from the crown to the edge, whereby some advantage is attained by placing the opening about thirty degrees from the center 15 of the crown, and maximum advantage is attained by placing the opening as close to the edge (about 'ten degrees) as is possible without interfering with the Weld. In order to facilitate mass production, it has been found most practical to place the opening with its axis located in a plane disposed at about thirty degrees with respect to the plane in which the edge and weld are located. By placing'the spud in such locations, the stress concentration which may occur will result in stresses that are no higher than the stresses C9 in smoothor continuous zones which are somewhat thinner.

The slight extra thickness adjacent the edge resulting from the drawing operation offsets any stress concentrations caused by the weld, wherefore a deliberate attempt is made to allow thickening to take place in this zonev In this manner, it is possible to manufacture a lightweight, high pressure spherical container with substantially uniform stresses throughout, in spite of thickness variation of the shells.

It has been found that spherical containers having a diameter of about twelve inches comprising hemispherical welded shells formed of steel blanks having a tensile strength of about 90,000 pounds per square inch and a thickness of about .168 inch can withstand a pressure of about 5000 pounds per square inch Without bursting, and are completely safe in service at pressures up to about 3000 pounds per square inch.

As various changes may be made in the form, construction and arrangement of the parts herein, without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense. 7

I claim:

1. A sphericalhigh pressure gas container comprising a pair of substantially hemispherical shells drawn from a high tensile steel blank of uniform thickness and deformed in the drawing process to reduce the thickness thereof about 10% at the crown and to increase the thickness thereof about 10% at the edge with the thickness decreasing progressively from the edge to the crown, each of said shells having an imperforate crownregionpsaid region including all portions of said shell'wherein the radii of said shell are disposed at an angle of greater than sixty degrees with respect to the plane in'which the edge is located, and one of said shells being formed with an opening having an axis passing through its center which is disposed at between ten and thirty degrees with respect.

to the plane in which the edge is located; a weld joining the edges of said shells in a gas tight manner; and an outlet fitting welded to said shell at said opening and formed with a passageway therethrough, whereby any stress concentrations caused by said opening are Within a portion of said shell having between a normal and an increased thickness.

2. A spherical high pressure gas container comprising a pair of'substantially hemispherical shells drawn from a high tensile steel blank of uniform thickness and deformed in the drawing process to reduce the thickness thereof about 10% at the crown and to increase the thickness thereof about 10% at the edge with the thickness decreasing progressively from the edge to the crown, each of said shells being formed with an opening having an axis passing through its center which is disposed at between References Cited in the file of this patent UNITED STATES PATENTS 1,966,241 Furrer July 10, 1934 2,113,060 Sandberg Apr. 5, 1938 2,410,323 Wellman Oct. 29, 1946 FOREIGN PATENTS 115,712 Australia Aug. 12, 1942 

